I spent $400 on mine, on sale, but I got the nicest 110V Lincoln Mig welder you could get at the time. It's a Migpack 135. It goes up to 135 amps, can weld 1/4" steel in one pass. It works great, has nice features, and is a breeze to use. All I needed to get was a gas bottle and a decent hood and gloves.
One thing to look for on the cheapies is a cold tip gun. The cheap ones do not switch the arc current, only the gas/wire feed, so it is a pain to get the arc switched. The nicer welders have a gas preflow that starts the gas a bit before you strike the arc. That keeps the weld ends nice.
You really do get what you pay for in a welder. I wouldn't spend less than $300 on a setup I was using on sheet metal, which is relatively difficult to weld. You need good control. I would stick with a name brand because parts like tips, rollers, wand jackets, etc. wear out and require replacement. You may also wish to add an aluminum kit later, which is only available for certain welders.
